Effectiveness of annual single doses of diethylcarbamazine citrate among bancroftian filariasis infected individuals in an endemic area under mass drug administration in Brazil

IgG4 antibodies to the recombinant filarial antigen Wb-Bhp-1 decrease dramatically following treatment of lymphatic filariasis

BACKGROUND

Lymphatic filariasis (LF) is a neglected tropical disease and a major cause of chronic disability. Improved diagnostic tests are needed because of long-term persistence of anti-filarial antibodies or circulating filarial antigenemia after treatments that clear microfilaremia. Here, we assess changes in levels of antibodies to the recombinant filarial antigens Wb-Bhp-1, Wb123, and Bm14 after anti-filarial treatment.

METHODOLOGY/PRINCIPAL FINDINGS

IgG4 antibodies to recombinant filarial antigens were assessed by ELISA. We tested serial plasma samples from a clinical trial in Papua New Guinea. Before treatment, 90%, 71% and 99% of participants had antibodies to Wb-Bhp-1, Wb123, and Bm14, respectively. Antibodies to Wb-Bhp-1 and Wb123, but not Bm14, were significantly higher in participants with persistent microfilaremia 24 months after treatment. Antibodies to all three antigens declined significantly by 60 months after treatment with ivermectin, diethylcarbamazine and albendazole despite circulating filarial antigen in 76% of participants. By 60 months follow up, antibodies to Wb-Bhp-1, Wb123, and Bm14 were detected in 17%, 7% and 90% of participants, respectively. Antibodies to Wb-Bhp-1 also declined more rapidly after treatment than antibodies to Bm14 in samples from a clinical trial conducted in Sri Lanka. We also tested archived serum samples from people living in filariasis-endemic communities in Egypt with different infection profiles. Antibodies to Wb-Bhp-1 were detected in 73% of microfilaremic people, 53% of amicrofilaremic people with circulating filarial antigen, and 17.5% of endemic individuals without microfilaria or circulating filarial antigen. Tests performed with legacy samples from India showed that few people with filarial lymphedema had antibodies to these recombinant antigens.

CONCLUSIONS

Antibodies to Wb-Bhp-1 and Wb123 are more closely correlated with persistent microfilaremia than circulating filarial antigenemia or antibodies to Bm14, and they clear more rapidly after anti-filarial treatment. Additional studies are needed to assess the value of Wb-Bhp-1 serology as a tool for determining the success of LF elimination efforts.

IgG4 antibodies against Bm14 as an evaluation tool of mass drug administration in a co-endemic area of Brugia timori and Wuchereria bancrofti

To evaluate the success of mass drug administration for lymphatic filariasis, WHO has recommended two rapid tests, Brugia Rapid (BR) to detect the presence of IgG4 antibodies against Brugia sp and Filariasis Test Strip (FTS) to detect antigens of Wuchereria bancrofti. As a country co-endemic for Brugia sp. and W. bancrofti, Indonesia needs a single diagnostic tool that can detect the exposure to both species. This study aimed to evaluate the efficacy of mass drug administration by measuring Bm14-specific IgG4 levels in blood samples of the population living in a co-endemic area of B. timori and W. bancrofti in Southwest Sumba Regency. A total of 132 plasma samples obtained before and one year after DEC-albendazole administration, which have been previously tested with BR and FTS, were examined for IgG4 against Bm14 using enzyme-linked immunosorbent assay. The results showed that before treatment all 32 individuals (100%) with BR+/ FTS+ were also positive for Bm14-specific IgG4, while in BR+ or FTS+ group there were >90% samples detected positive. At one year after treatment, positive results for Bm14-specific IgG4 were still detected in 96.9% samples with BR+/ FTS+, 78.8% samples with BR+/ FTS- and 82.9% samples with BR-/ FTS+. On the other hand, the BR-/ FTS- group also had high rate of Bm14-specific IgG4 positivity either before treatment (62,5%) and at one year after treatment (43.8%). The lowest decrease of Bm14-specific IgG4 positivity at one year after treatment was shown in the double positive group (3.1%), while the highest was in the double negative group (18.7%). The measurement of IgG4 against Bm14 has the potential as a sensitive diagnostic tool to evaluate the success of MDA in the areas co-endemic for B. timori and W. bancrofti.

Genome editing as control tool for filarial infections

Human filarial infections are vector-borne nematode infections, which include lymphatic filariasis, onchocerciasis, loiasis, and mansonella filariasis. With a high prevalence in developing countries, filarial infections are responsible for some of the most debilitating morbidities and a vicious cycle of poverty and disease. Global initiatives set to eradicate these infections include community mass treatments, vector control, provision of care for morbidity, and search for vaccines. However, there are growing challenges associated with mass treatments, vector control, and antifilarial vaccine development. With the emergence of genome editing tools and successful applications in other infectious diseases, the integration of genetic editing techniques in future control strategies for filarial infections would offer the best option for eliminating filarial infections. In this review, we briefly discuss the mechanisms of the three main genetic editing techniques and explore the potential applications of these powerful tools to control filarial infections.